P.Cykes and Inktail Nekogami both had some very similar suggestions involving Globbles trick or treating, so I mashed them together to make this sequence.
Globbles doesn't really get how any of this works but at least she knew to ring the bell. Those candy bowls they were holding while most of them still had hands must be trophies or articles of attire. Probably the latter--everyone was costume after all, before their costumes dissolved.
Only a true witch gives out those types of treats.